Detection and control of the pathogenic microorganisms in water, especially in portable water, is a big concern as these health-affected contaminants in potable water may cause a fatal outbreak especially in a densely-populated city [1].
There are existing conventional laboratory methods for detecting certain known types of pathogenic microorganisms. These conventional microbiological laboratory methods have some intrinsic limits such as long processing time, and high cost. Furthermore, they are laborious with a need for skilled technicians and ineffective for onfield monitoring.
Moreover, there is a limit to the types of microorganisms that conventional laboratory methods are able to detect. These methods typically require the following steps: sampling, culturing, isolation, staining and quantification by microscopic method. However, some pathogens, such as Cryptosporidium parvum (C. parvum) and Giardia lamblia (G. lamblia), are impossible to culture. This is an important constraint for these conventional methods because quite a few waterborne outbreaks are in fact caused by emerging pathogenic microorganisms or even modified organisms—which conventional laboratory methods are not able to detect.
Currently, the most widely accepted protocol for their analysis is US-EPA 1623 method [3]. First, the water is collected and shipped to a laboratory in a volume ranging from 10 to 1000 L, depending on the expected organism level. The water sample is then sent to a filter and is concentrated into a smaller volume. Pathogens can be then further concentrated through centrifugation and screened out by the use of an immune-magnetic separation method [4]. The final concentrated organisms are then stained and manually counted by a fluorescence microscope. The time required by this method or other conventional microbiological methods to yield results is normally from 24 to 72 hours, which is not practical to provide an event warning.
In recent years, some other methods like the polymerase chain reaction (PCR) and flow cytometry are also used for the water pathogens detection. Note that flow cytometry requires fluorescent labeling for particle identification. However, many microorganisms in water do not have the specific stain chemicals for labeling. Although flow cytometry may detect a scattering intensity of a particle, it is used for counting particle count instead of identifying particles (such as bacteria) since the scattering intensity is mostly based on the particle size—which would not be reliable for particle identification. Therefore, it is difficult to use the flow cytometry for pathogen detection in water. Moreover, these methods are still laboratory based, labor-intensive, and high cost due to the consumption of the bio-reagents.
Therefore, there is a need for an improved method and device for detecting and identifying pathogens in water to allow real-time and on-site monitoring of waterborne pathogens. It is also desired to develop a modern water risk management system and method with an automated working process with low-cost, fast, reliable detection of pathogenic microorganisms in water.